The long-term goal of this work is to develop a feasible acoustic noise control (ANC) system specifically tailored for MRI environment. The specific objective of this proposal is to design, construct and implement a working active noise reduction prototype that can substantially reduce the sound pressure levels inside the MRI bore. This requires an in-depth understanding of the true characteristics of MRI sound fields. The central hypothesis of this study is that the intense sound energy produced by the operation of MRI is strongly correlated with gradient pulses; and thus it can be controlled by an active ANC system that does not impede the primary imaging operation. It is our belief that the tonal behavior of the MRI sound spectrum revealed from our preliminary studies is well suitable for active noise cancellation techniques that normally work well for predictable harmonic signals. The rationale is that the ability of suppression acoustical noise in MRI is expected to seed new control algorithms that can be evaluated for prototyping. Active noise control is conceptually appealing because it avoids major reconstruction of the core MRI system. Furthermore, the successful implementation of this control system will remove, or at least diminish, acoustic noise as one of the barriers at very high field strength applications (> 7 Tesla), and hence allow for even higher fields to be employed for medical imaging and research in the future. In this proposed studies, the following specific aims will be pursued: 1) Identify and characterize the nature of controllable MRI noise - to investigate the radiated sound pressure characteristics, clarify their functional relationships with the gradient pulses of various imaging sequences, and identify significant features that can be controlled. 2) Determine feasible sensing and actuation concepts - to develop feasible sensing and actuation approaches that will be effective in suppressing the dominant acoustic noise signatures inside the MRI scanner bore. 3) Develop an ANC system - to design and implement a prototype for active ANC in the vicinity of the patient's ear and mouth. [unreadable] [unreadable]